1. Field of the Invention
The present invention relates generally to methods of track counting for a disk player and track counter circuits therefor, and more specifically, to a method of accurately counting the number of tracks a pickup has crossed and a circuit therefor, in an optical disk player which scans an optical disk across the tracks with a plurality of laser beams.
2. Description of the Background Art
In order to selectively reproduce a desired item from a compact disk for music which records a plurality of music items, the pickup must be quickly moved on the first track from which the item starts. While the pickup is thus moved to a prescribed position on the disk across the tracks, a reproduction output obtained by a reproduction beam is detected, and the number of tracks the pickup has crossed is counted in response to changes in the level of the detected reproduction signal. Stopping the pickup once the number of counted tracks reaches a prescribed number permits the pickup to move quickly to the first track from which the desired item is recorded.
In this case, however, since the pickup moves at a high speed and pits are intermittently formed on the track, a reproduction beam sometimes passes spaces between pits without irradiating the pits. At the time, the number of tracks the pickup has crossed is erroneously counted, and therefore the pickup cannot be stationed accurately at a desired position.
A method for solving such a problem disclosed in Extended Abstracts (The 50th Autumn Meeting, 1989); The Japan Society of Applied Physics, No. 3, page 977 takes advantage of the periodicity of track crossing pulses generated in response to changes in the level of a reproduction signal and supplements a dropped out pulse when the periodicity is disturbed by the dropped out crossing pulse. If the pickup accesses at a high speed, however, a series of crossing pulses often drop out, and completely supplementing such dropout pulses would not be possible.